range.go

// Copyright 2014-2015 The Dename Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

// Copyright 2012 Suryandaru Triandana <syndtr@gmail.com>
// Modified in 2015 by Andres Erbsen <andreser@yahoo-inc.com>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package kv

// Range is a key range.
type Range struct {
	// Start of the key range, included in the range.
	Start []byte

	// Limit of the key range, not included in the range. nil indicates no limit.
	Limit []byte
}

// IncrementKey returns the lexicographically first DB key which is greater
// than all keys prefixed by "prefix". Following the Range.Limit convention,
// IncrementKey may return nil, a sentinel value that is to be interpreted as
// greater than all keys.
func IncrementKey(prefix []byte) []byte {
	for i := len(prefix) - 1; i >= 0; i-- {
		c := prefix[i]
		if c < 0xff {
			limit := make([]byte, i+1)
			copy(limit, prefix)
			limit[i] = c + 1
			return limit
		}
	}
	return nil
}

// BytesPrefix returns key range that satisfy the given prefix.
func BytesPrefix(prefix []byte) *Range {
	return &Range{prefix, IncrementKey(prefix)}
}